The present invention relates to valves and particularly to automatic valves and the method for using same with filters operating with filter aid material, such as diatomaceous earth, in order to prevent such filters from transferring fine particles to the filtered fluid area at the beginning of the filtering operation when the cake is not yet uniformly disposed around the filter element and to assist the distribution and the uniformity of the filter aid material on the filter element surface area and in many other applications.
Automatic valves have many industrial uses and are common in all kinds of assemblies. Most of the valves are manually operated. In order to operate the valves automatically, an electric or hydraulic motor, or an actuator, must be mounted on the valves to shift the interconnection and communication between the valve passages. Actuators and electric motors are both unwieldy, expensive and complex. There are automatic valves with timing mechanism for the use in a system with a Diatomaceous Earth filter, e.g. U.S. Pat. No. 5,899,231 to Drori which discloses an automatic three way valve with timing mechanism for delaying the opening of the flow. U.S. Pat. No. 6,171,495 to Drori also discloses an automatic three way valve with a time delay mechanism. The problem regarding the distribution of filter aid material on the filter element surface in an homogeneous layer is known in the field.
It is the object of the present invention to provide an improved automatic valve constructed to transfer for a pre-determined time low flow at the beginning of operation to assist the build-up of a uniform layer of the filter aid material porous material on the filter element surface in order to receive fine filtration and to prevent fine particles to penetrate through the filter element. After such a predetermined time, the valve is open automatically to full flow.
In accordance with a broad aspect of a preferred embodiments of the present invention, there is provided a method and apparatus incorporating an automatic valve, preferably a three-way valve constructed of a housing having inlet, outlet and drain passages and including an internal close-open timing mechanism. The timing mechanism is adjusted to a predetermined period of time in order to close the drain passage and open the outlet passage or to close the outlet passage and open the drain passage. The opening and closing of passages occurs automatically after a predetermined period of time in response to the starting or stopping of an external source of pressurized fluid such as a pump which provides pressurized fluid to the three way valve.
The automatic three way valve, in accordance with the present invention, comprises a housing having inlet, outlet and drain passages and an hydraulic unit connected to the housing and to an internal movable shaft moving with two stops set apart a predetermined distance and between drain passage and outlet passage. A sealing flange is located around the movable shaft and disposed between the two stops. The stops are adjusted with respect to each other so that the sealing flange moves into sealing relationship with either the outlet or the drain passages. The movable shaft is adjusted to move linearly and freely through a central aperture located on the central area of the sealing flange. The movement of the shaft is limited to the distance traveled until one of the two stops pushes against the sealing flange in order to open either one of the outlet or drain passages and closing the other one of the passages. Controlling the period of time between the entering of pressurized fluid to the inlet passage of the three way valve from a source of pressurized fluid which flows through the inlet passage to the drain passage until the opening of the outlet passage and the closing of the drain passage is an important aspect of the present invention. This period of time is controlled by adjusting the distance between the two stops located on the movable shaft and the size of the passage of pressurized fluid located on the hydraulic unit. A control valve, preferably of a relatively small size, is connected to the pressurized fluid passage located on the hydraulic unit. The control valve is provided in order to control the size of the opening of the pressurized fluid passage and the period of time between the opening or closing of the pressurized fluid flow to the valve and the time of the opening or closing of the outlet or the drain passages.
The method and apparatus of the automatic three way valve described and claimed in the present invention are preferably for the use with filters using filter aid material, such as diatomaceous earth (DE), to prevent penetration of fine particles, usually sediments, to the filtered fluid area which would result in the filtered fluid being contaminated with the fine particles during the first stages of filtration when the cake of filter aid material has still not yet or not completely built itself up around the filter element. The present invention provides features allowing the fine particles to drain separately from the filtered fluid for a predetermined time. After the predetermined period of time has passed, the drain passage automatically closes and the flow of filtered fluid from the filter is directed through the outlet passage to a filtered fluid collection area, such as a pool.
In accordance with a broad aspect of the preferred embodiment of the present invention, there is provided a method and apparatus incorporating an automatic valve adapted to reduce the flow for a pre-determined time in order to assist the filter aid material in the filter to be distributed uniformly on the filter element surface area and automatically open the full flow after said filter aid material is uniformly distributed on the filter element.